The Effect of Aging on Nitric Oxide Production during Cerebral Ischemia and Reperfusion in Wistar Rats and Spontaneous Hypertensive Rats: An In Vivo Microdialysis Study.

Nitric oxide (NO) is involved in the pathogenesis of cerebral ischemic injury. Here, we investigated the effects of aging on NO production during cerebral ischemia-reperfusion (IR). Male Wister rats (WRs) were assigned to 12-month-old (older; n = 5) and 3-month-old (younger; n = 7) groups. Similarly, male spontaneous hypertensive rats (SHRs) were allocated to 12-month-old (older; n = 6) and 3-month-old (younger; n = 8) groups. After anesthesia, their NO production was monitored using in vivo microdialysis probes inserted into the left striatum and hippocampus. Forebrain cerebral IR injuries were produced via ligation of the bilateral common carotid arteries, followed by reperfusion. The change in the NO3- of the older rats in the SHR groups in the striatum was less compared to that of the younger rats before ischemia, during ischemia, and after reperfusion (p < 0.05). In the hippocampus, the change in the NO3- of the older rats in the SHR groups was lower compared to that of the younger rats after reperfusion (p < 0.05). There were no significant differences between the two WR groups. Our findings suggested that aging in SHRs affected NO production, especially in the striatum, before and during cerebral ischemia, and after reperfusion. Hypertension and aging may be important factors impacting NO production in brain IR injury.

Synthesis of a plasmenylethanolamine.

A concise synthesis of a plasmenylethanolamine (PlsEtn-[16:0/18:1 n-9]), known as antioxidative phospholipids commonly found in cell membranes, has been achieved from an optically active known diol through 8 steps. The key transformations for the synthesis of PlsEtn-[16:0/18:1 n-9] are (1) regio- and Z-selective vinyl ether formation via the alkylation of a lithioalkoxy allyl intermediate with an alkyl iodide, and (2) a one-pot phosphite esterification-oxidation sequence to construct the ethanolamine phosphonate moiety in the presence of the vinyl ether functionality. The piperidine salt of synthetic PlsEtn-[16:0/18:1 n-9] was desalinated through reversed-phase high-performance liquid chromatography purification.

Naratriptan in the Prophylactic Treatment of Cluster Headache.

Objective Naratriptan has been reported to reduce the frequency of cluster headache. The purpose of this study was to determine whether naratriptan is effective as a prophylactic treatment for cluster headache in Japan. Methods We retrospectively reviewed all 43 patients with cluster headache who received preventive treatment with naratriptan from April 2009 to April 2015. The International Classification of Headache Disorders, 3rd Edition (beta version) (ICHD-3 beta) was used to diagnose cluster headache. This study was conducted at 3 centers (Department of Neurology, Saitama Medical University; Saitama Neuropsychiatric Institute; Saitama Medical University International Medical Center). Patients were recruited from these specialized headache outpatient centers. Naratriptan was taken before the patient went to bed. Results The study population included 30 men (69.8%) and 13 women (30.2%). Twenty-two cases received other preventive treatments (51.2%), while 21 cases only received naratriptan (48.8%). Among the 43 cases, 37 patients (86.0%) achieved an improvement of cluster headache on naratriptan. Conclusion Naratriptan has been suggested as a preventive medicine for cluster headache because of the longer the biological half-life in comparison to other triptans. The internal use of naratriptan 2 hours before attacks appears to achieve a good response in patients with cluster headache.

Nitric oxide production during cerebral ischemia and reperfusion in eNOS- and nNOS-knockout mice.

The purpose of this study was to clarify the kinetics of nitric oxide (NO) induced by either endothelial NO synthase (eNOS) or neuronal NO synthase (nNOS) after transient global forebrain ischemia. We investigated NO production and ischemic changes to hippocampal CA1 neurons in eNOS knockout (-/-) mice and nNOS (-/-) mice during cerebral ischemia and reperfusion. NO production was continuously monitored by in vivo microdialysis. Global forebrain ischemia was produced by occlusion of both common carotid arteries for 10 minutes. Levels of nitrite (NO(2)(-)) and nitrate (NO(3)(-)), as NO metabolites, in dialysate were determined using the Griess reaction. Two hours after the start of reperfusion, animals were perfused with 4% paraformaldehyde. Hippocampal CA1 neurons were divided into three phases (severely ischemic, moderately ischemic, surviving), and the ratio of surviving neurons to degenerated neurons was calculated as the survival rate. The relative cerebral blood flow (rCBF) was significantly higher in nNOS (-/-) mice than in control mice after reperfusion. Levels of NO(3)(-) were significantly lower in eNOS (-/-) mice and nNOS (-/-) mice than in control mice during ischemia and reperfusion. NO(3)(-) levels were significantly lower in nNOS (-/-) mice than in eNOS (-/-) mice after the start of reperfusion. Survival rate tended to be higher in nNOS (-/-) mice than in control mice, but not significantly. These in vivo data suggest that NO production in the striatum after reperfusion is closely related to activities of both nNOS and eNOS, and is mainly related to nNOS following reperfusion.

Efficacy of temozolomide is correlated with 1p loss and methylation of the deoxyribonucleic acid repair gene MGMT in malignant gliomas.

Promoter methylation of the deoxyribonucleic acid (DNA) repair gene, O(6)-methylguanine-DNA methyltransferase (MGMT), is associated with improved outcome of patients with glioblastoma multiforme and anaplastic astrocytoma treated with temozolomide (TMZ). Molecular genetic analysis of loss of heterozygosity (LOH) of 1p, 19q, or 10q, p53 mutation, and MGMT promoter methylation was performed in 44 assessable tumor specimens obtained from 46 patients with recurrent malignant gliomas, including 21 with glioblastoma multiforme, 17 with anaplastic astrocytoma, and eight with anaplastic oligoastrocytoma, which have heterogeneous features and variable histological diagnosis, to assess the correlation with the response to TMZ. LOHs of 1p and 19q, and MGMT promoter methylation showed positive correlations with the clinical response to TMZ therapy (p < 0.005, 0.05, and 0.05, respectively; Fisher's exact test). In addition, LOH of 1p and MGMT promoter methylation were associated with longer progression-free survival (p < 0.05 and 0.05, respectively; Cox regression analysis). LOH of 1p in the heterogeneous population of malignant gliomas may be one of the important factors besides MGMT methylation that predict better outcome in patients treated with TMZ.

Role of nitric oxide scavenging in vascular response to cell-free hemoglobin transfusion.

Modified Hb solutions have been developed as O(2) carrier transfusion fluids, but of concern is the possibility that increased scavenging of nitric oxide (NO) within the plasma will alter vascular reactivity even if the Hb does not readily extravasate. The effect of decreasing hematocrit from approximately 30% to 18% by an exchange transfusion of a 6% sebacyl cross-linked tetrameric Hb solution on the diameter of pial arterioles possessing tight endothelial junctions was examined through a cranial window in anesthetized cats with and without a NO synthase (NOS) inhibitor. Superfusion of a NOS inhibitor decreased diameter, and subsequent Hb transfusion produced additional constriction that was not different from Hb transfusion alone but was different from the dilation observed by exchange transfusion of an albumin solution after NOS inhibition. In contrast, abluminal application of the cross-linked Hb produced constriction that was attenuated by the NOS inhibitor. Neither abluminal nor intraluminal cross-linked Hb interfered with pial arteriolar dilation to cromakalim, an activator of ATP-sensitive potassium channels. Pial vascular reactivity to hypocapnia and hypercapnia was unaffected by Hb transfusion. Microsphere-determined regional blood flow indicated selective decreases in perfusion after Hb transfusion in the kidney, small intestine, and neurohypophysis, which does not have tight endothelial junctions. Administration of a NOS inhibitor to reduce the basal level of NO available for scavenging before Hb transfusion prevented further decreases in blood flow to these regions compared with NOS inhibition alone. In contrast, blood flow to skeletal and left ventricular muscle increased, and cerebral blood flow was unchanged after Hb transfusion. This cross-linked Hb tetramer is known to appear in renal lymph but not in urine. We conclude that cell-free tetrameric Hb does not scavenge sufficient NO in the plasma space to significantly affect baseline tone in vascular beds with tight endothelial junctions but does produce substantial constriction in beds with porous endothelium. The data support increasing the molecular size of Hb by polymerization or conjugation to limit extravasation in all vascular beds to preserve normal vascular reactivity.

A peroxisome proliferator-activated receptor-gamma agonist reduces infarct size in transient but not in permanent ischemia.

BACKGROUND AND PURPOSE: Activators of peroxisome proliferator-activated receptor-gamma (PPARgamma), a member of the PPAR family, increase levels of CuZn-superoxide dismutase (SOD) in cultured endothelium, suggesting a mechanism by which it may exert its protective effect within the brain. These properties raise the question of whether a PPARgamma agonist may be neuroprotective in models of ischemia without reperfusion, in which oxidative injury is less prevalent. METHODS: In 2 groups of rats, 90 minutes of middle cerebral artery (MCA) occlusion was followed by 1 day of reperfusion, with 1 group receiving pioglitazone (a PPARgamma agonist) starting 72 hours before MCA occlusion (MCAO) and continuing through the day of occlusion, whereas the other group received vehicle only. In 2 comparable groups, the MCA was occluded permanently. One day after occlusion, the animals were tested neurologically and infarct volumes were calculated. In a separate group, rats were treated with pioglitazone or vehicle for 4 days. Tissue was obtained from the cortex and the striatum 2 hours into reperfusion after 90 minutes of MCAO, and the tissue was examined for CuZn-SOD by Western blot. RESULTS: Results show a significant reduction in infarct size in the treated rats, with transient MCAO but not permanent MCAO. There was also an improvement in neurological score in the treated animals after transient MCAO. The level of CuZn-SOD was increased in the cortex in treated animals. CONCLUSIONS: These data, which show that a PPARgamma agonist reduces infarct size in transient but not permanent MCAO, suggest that the role of PPARgamma is specific to events occurring during reperfusion. Our data point to CuZn-SOD as the mediator of this neuroprotection.